1. Field of the Invention
This invention relates to a flexible tube for endoscope for use in an insertion portion to be inserted into a lumen, and an endoscope including the endoscopic flexible tube.
2. Description of the Related Art
For example, according to Jpn. Pat. Appln. KOKAI Publication No. 2003-19109, a variable-pitch spiral tube is provided in a flexible tube to adjust the flexibility (bendability) of the flexible tube of an insertion portion. The spiral tube is located inside the flexible tube out of alignment with its central axis. The flexibility of the flexible tube can be changed by narrowing or expanding the pitch of the spiral tube.